To date, asphalt compositions are widely used for road paving, waterproofing sheets, sound-proof sheets, roofing, and other applications. Numerous attempts have been made to improve the properties of asphalt by adding various polymers to the asphalt. Ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, rubber latexes, block copolymers composed of conjugated dienes and vinyl aromatic hydrocarbons, and the like are used as such polymers.
Recently, there are increasing demands for asphalt compositions that have excellent strength and wear resistance because of the increasing number and increasing speed of road going vehicles and other such reasons. Accordingly, a higher softening point and mechanical strength such as elongation, modulus, and the like are required and, therefore, dispersibility in asphalt compositions is required of block copolymers.
For example, Patent Document 1 discloses an asphalt composition comprising a copolymer that is composed of a conjugated diene and a vinyl aromatic hydrocarbon and that has a specific structure.
Patent Document 2 discloses an asphalt composition for roofing shingles, comprising a filler and a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene.
Patent Document 3 discloses an asphalt composition comprising a blowing agent as an additive, and Patent Document 4 discloses a vulcanized asphalt composition.